NAMS 2002 Workshop - ICOM 2008

permeability, defined as water permeability multiplied by viscosity in bulk water,
was not constant and increased with a decrease in pore sizes, that is, the water
permeation mechanism was found to be different from the viscous flow. This is
probably because water molecules, which are tightly bound to the hydrophilic
surface of TiO2 membranes and were confirmed by measuring non-freezing and
bound water in TiO2 powders, shows different temperature dependence from
that in bulk.
Rejection of neutral solutes (raffinose, PEG1000) decreased with temperature in
the range of 30-90 C, while that of electrolytes(MgCl2, NaCl) were approximately
constant. Based on Spiegler-Kedem equation, reflection coefficients for both
solutes were successfully fitted to be independent of permeation temperatures.
Permeability coefficients (P) of electrolytes were found to show the same
temperature dependence as Lp, that is, P increased almost linearly to Lp. On the
other hand, P of neutral solutes showed larger temperature dependence than Lp,
that is the neutral solutes were found to be transported in activated diffusion. The
transport mechanism of neutral and electrolyte solutes, which are molecular
sieving and charge effect, respectively, are found to be responsible for the
temperature dependence.
[1] N. Amar, H. Saidani, A. Deratani, J. Palmeri, Langmuir, 23(2007) 2937.
[2] T. Tsuru, S. Izumi, T. Yoshioka, M. Asaeda, AIChE Journal, 46 (2000) 565-574.
[3] T. Tsuru, Separation and Purification Methods, 30 (2001) 191-220.
[4] T. Tsuru, J. Sol-Gel Sci., Tech., in press.
[5] T. Tsuru, D. Hironaka, T. Yoshioka, M. Asaeda, Sep. Purif. Tech., 25 (2001) 307-314.
[6] T. Tsuru, T. Hino, T. Yoshioka, M. Asaeda, J. Membr. Sci., 186 (2001) 257-265.